The present invention relates to a high superabsorbent content fluff/wood pulp absorbent. More particularly, the present invention relates to a high superabsorbent containing absorbent which has increased wicking ability.
Perhaps the oldest known liquid absorbents to man are those products made from cotton, wood pulp or fluff and other natural materials. These materials have been used routinely to absorb liquids, and in particular, body fluids, in connection with personal care and other absorbent articles such as diapers, training pants, incontinence garments, sanitary napkins, bandages, and the like. As the development of these products has progressed, so too has the need for increased liquid retention capacity. One means for increasing the liquid retention capabilities of such products is through the addition of superabsorbents which are also referred to as hydrogels and hydrocolloids. This is particularly true in the case of diapers, training pants and incontinence garments. As these products have become more and more sophisticated, the manufacturers of these products have reduced the amount of wood pulp or fluff in the absorbent layers of these materials and replaced the fluff with varying amounts of superabsorbent.
As the amount of superabsorbent has increased in these absorbent structures, a problem called gel-blocking has arisen. Early superabsorbents were made in particle form and while being capable of absorbing many times their own weight in liquid such as water and urine, would not hold their particle or generally spherical shape as they absorbed liquid. Instead, they would turn into a mushy gel which would swell, fill the voids between the wood pulp fibers and quickly turned the structure into a gelled mess. This is now referred to as gel blocking. As a result of this gel blocking, there were no longer any pores or capillaries through which to transport additional quantities of liquid. Consequently, using diapers as an example, despite the overall high liquid retention capability of the absorbent, very little of the liquid-absorbing capacity could be utilized because of the gel-blocking problem. After a first or second insult, the area receiving the liquid would gel block, the liquid would not absorb and sometimes run off the surface of the gel mass and would even leak out of the diaper. Because of this, there was only a finite amount of superabsorbent which could be added to the absorbent structure.
As superabsorbent work developed, superabsorbent particles were created which had a high liquid capacity and a higher gel strength in the sense that the particles would absorb greater amounts of liquid and still retain their generally spherical shape. As a result, the amount of superabsorbent which could be added to the absorbent portion of a personal care absorbent product, such as a diaper, increased. Manufacturers could, therefore, remove more wood pulp and replace it with superabsorbent. In addition, the manufacturers found that they could more highly compress the absorbent to create a much thinner diaper. Here again, however, a problem arose with the ability of the absorbent in the diaper to utilize its entire capacity.
With the new high gel strength, higher capacity superabsorbents the problem with gel blocking decreased, but a new problem took its place. As the new superabsorbents swelled upon absorbing liquid, their diameters would greatly increase. Highly compressing the fluff/superabsorbent composite absorbents helped to maintain the liquid-transporting properties of the absorbent, but there was still a problem with the full utilization of the absorbent's capacity. This was because as the superabsorbent particles swelled, they pushed the absorbent structure open and apart. On a microscopic scale, this expansion created large voids within the absorbent structure, thereby greatly reducing the capillary action within the absorbent and thus the ability of the absorbent to transport and wick liquids away from the insult zone to other areas of the absorbent composite in the diaper so that the capacity of the diaper could be more fully utilized. In essence, the liquid transport/wicking problem went from an absorbent which gel blocked and had virtually no capillaries to transport liquid to an absorbent which became too open and, therefore, did not have sufficient capillary action to wick and transport the liquids away from the insult zone. As a result, there again became an upper limit as to the amount of superabsorbent which could be added to a fluff-based absorbent. This problem was exacerbated by the fact that existing pulp does not have sufficient surface area per unit mass to compensate for the disruptions in the capillarity due to the swelling of the superabsorbent particles.
It is, therefore, an object of the present invention to provide an absorbent structure which can utilize wood pulp with a high loading of superabsorbent.
It is another object of the present invention to create a wood pulp/superabsorbent composite which has increased capillarity and wicking action thereby making an absorbent structure which can more efficiently utilize its liquid-retentive capabilities. These and other objects of the present invention will become more apparent on a further review of the following specification and claims.